class ActiveSupport::Cache::MemCacheStore
A cache store implementation which stores data in Memcached: memcached.org/
This is currently the most popular cache store for production websites.
Special features:
-
Clustering and load balancing. One can specify multiple memcached servers, and MemCacheStore will load balance between all available servers. If a server goes down, then MemCacheStore will ignore it until it comes back up.
MemCacheStore implements the Strategy::LocalCache strategy which implements an in-memory cache inside of a block.
Constants
- ESCAPE_KEY_CHARS
Public Class Methods
Creates a new MemCacheStore object, with the given memcached server addresses. Each address is either a host name, or a host-with-port string in the form of “host_name:port”. For example:
ActiveSupport::Cache::MemCacheStore.new("localhost", "server-downstairs.localnetwork:8229")
If no addresses are specified, then MemCacheStore will connect to localhost port 11211 (the default memcached port).
# File lib/active_support/cache/mem_cache_store.rb, line 76 def initialize(*addresses) addresses = addresses.flatten options = addresses.extract_options! super(options) unless [String, Dalli::Client, NilClass].include?(addresses.first.class) raise ArgumentError, "First argument must be an empty array, an array of hosts or a Dalli::Client instance." end if addresses.first.is_a?(Dalli::Client) @data = addresses.first else mem_cache_options = options.dup UNIVERSAL_OPTIONS.each{|name| mem_cache_options.delete(name)} @data = self.class.build_mem_cache(*(addresses + [mem_cache_options])) end end
Public Instance Methods
Clear the entire cache on all memcached servers. This method should be used with care when shared cache is being used.
# File lib/active_support/cache/mem_cache_store.rb, line 137 def clear(options = nil) rescue_error_with(nil) { @data.flush_all } end
Reads multiple values from the cache using a single call to the servers for all keys. Options can be passed in the last argument.
# File lib/active_support/cache/mem_cache_store.rb, line 95 def read_multi(*names) options = names.extract_options! options = merged_options(options) keys_to_names = Hash[names.map{|name| [normalize_key(name, options), name]}] raw_values = @data.get_multi(keys_to_names.keys) values = {} raw_values.each do |key, value| entry = deserialize_entry(value) values[keys_to_names[key]] = entry.value unless entry.expired? end values end
Get the statistics from the memcached servers.
# File lib/active_support/cache/mem_cache_store.rb, line 142 def stats @data.stats end
Private Instance Methods
# File lib/active_support/cache/mem_cache_store.rb, line 192 def deserialize_entry(raw_value) if raw_value entry = Marshal.load(raw_value) rescue raw_value entry.is_a?(Entry) ? entry : Entry.new(entry) end end
# File lib/active_support/cache/mem_cache_store.rb, line 184 def escape_key(key) ActiveSupport::Deprecation.warn(" `escape_key` is deprecated and will be removed from Rails 5.1. Please use `normalize_key` which will return a fully resolved key or nothing. ".strip_heredoc) key end
Memcache keys are binaries. So we need to force their encoding to binary before applying the regular expression to ensure we are escaping all characters properly.
# File lib/active_support/cache/mem_cache_store.rb, line 176 def normalize_key(key, options) key = super.dup key = key.force_encoding(Encoding::ASCII_8BIT) key = key.gsub(ESCAPE_KEY_CHARS){ |match| "%#{match.getbyte(0).to_s(16).upcase}" } key = "#{key[0, 213]}:md5:#{Digest::MD5.hexdigest(key)}" if key.size > 250 key end
# File lib/active_support/cache/mem_cache_store.rb, line 199 def rescue_error_with(fallback) yield rescue Dalli::DalliError => e logger.error("DalliError (#{e}): #{e.message}") if logger fallback end